BIFUNCTIONAL OPIOID PEPTIDE ANALGESICS

描述（由申请人提供）：临床迫切需要开发具有新型生物活性的阿片类镇痛药，这些镇痛药缺乏现有阿片类药物的限制性副作用。研究表明，阿片受体拮抗剂、大麻素（CB1）拮抗剂、P物质（NK1）拮抗剂或阿片受体样（ORL1）拮抗剂的联合施用可以降低阿片受体拮抗剂产生镇痛耐受性和身体依赖性的倾向。在此证据的基础上，我们建议开发具有系统活性的双功能化合物，这些化合物具有阿片受体激动剂/阿片受体拮抗剂-，阿片受体激动剂/CB1拮抗剂-，阿片受体激动剂/NK1拮抗剂-或阿片受体激动剂/ORL1拮抗剂的混合特征，作为镇痛药，预计将产生很少或没有耐受性和身体依赖性，并且具有低成瘾倾向。具有这些特征的双功能配体具有系统活性并能够穿过血脑屏障（BBB），迄今尚未报道。双功能配体的设计将基于将各种拮抗剂药物载体（多肽和非多肽）直接或通过短连接体连接到强效和高选择性的阿片激动剂肽[Dmt1]DALDA （h -Dmt- d - arg - ph - lys - nh2; Dmt = 2'6'-二甲基酪氨酸）的不同位点，而不干扰两种成分的激动剂/拮抗剂特性。这将通过仔细考虑两种成分的已知结构-活性关系（SAR）以及配体对接受体结合位点的分子模型来完成。[Dmt1]DALDA因其镇痛效价高、口服生物利用度高、稳定性好、消除半衰期长、作用持续时间长而被选择作为激动剂。有证据表明，所提出的[Dmt1]DALDA拮抗剂偶联物将能够渗透到中枢神经系统，因为[Dmt1]DALDA成分将赋予整个双功能结构的血脑屏障穿越能力。这已经被证明是两种已经制备的阿片类激动剂/d拮抗剂的情况，当皮下给药时产生有效的中枢介导的抗感觉（s.c）。双功能配体将通过固相合成或固相和溶液肽合成技术的结合来制备。化合物的体外生物学特性将通过受体结合试验、分离组织试验和[35S]GTP？使用含有单表达的阿片样物质，d阿片样物质，CB1， NK1或ORL1受体的HEK细胞进行S结合试验。它们的镇痛效力将在急性疼痛模型（甩尾和热板）和作为神经性疼痛模型的慢性收缩损伤模型中确定。此外，这些化合物产生镇痛耐受性、身体依赖、成瘾（场所条件反射范例）、便秘和呼吸抑制的倾向将被检查。

DESCRIPTION (provided by applicant): There is an urgent clinical need for the development of opioid analgesics with novel biological activity profiles that lack the limiting side effects of the currently available opiates. It has been shown that the propensity of ¿ opioid agonists to produce analgesic tolerance and physical dependence can be reduced by co-administration of a d opioid antagonist, a cannabinoid (CB1) antagonist, a substance P (NK1) antagonist or an opioid receptor like (ORL1) antagonist. On the basis of this evidence we propose to develop systemically active, bifunctional compounds with a mixed ¿ opioid agonist/d opioid antagonist-, ¿ agonist/CB1 antagonist-, ¿ agonist/NK1 antagonist- or ¿ agoist/ORL1 antagonist profile as analgesics expected to produce little or no tolerance and physical, dependence, and with low addiction liability. Bifunctional ligands with these profiles that are systemically active and able to cross the blood-brain barrier (BBB) have not been reported to date. The design of the bifunctional ligands will be based on attachment of the various antagonist pharmacophores (peptides and non-peptides) to various sites of the potent and highly selective ¿ opioid agonist peptide [Dmt1]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2; Dmt = 2'6'- dimethyltyrosine) either directly or via a short linker in a way that does not interfere with the agonist/antagonist properties of the two components. This will be done by careful consideration of known structure-activity relationships (SAR) of the two components in conjunction with molecular modeling of ligand docking to the receptor binding sites. [Dmt1]DALDA was chosen as the ¿ agonist component because of its high analgesic potency, oral bioavailability, high stability, long elimination half-life and long duration of action. There is evidence to indicate that the proposed [Dmt1]DALDA-antagonist conjugates will be able to penetrate into the central nervous system because the [Dmt1]DALDA component will confer blood-brain barrier crossing ability upon the entire bifunctional construct. This has been shown to be the case with two already prepared ¿ opioid agonist/d antagonists of this type which produced potent centrally mediated antinociception when given subcutaneously (s.c.). The bifunctional ligands will be prepared by solid-phase synthesis or by a combination of solid-phase- and solution peptide synthesis techniques. The in vitro biological profiles of the compounds will be determined by performing receptor binding assays, isolated tissue assays and [35S]GTP?S binding assays using HEK cells containing singly expressed ¿ opioid, d opioid, CB1, NK1, or ORL1 receptors. Their analgesic potencies will be determined in acute pain models (tail-flick and hot plate) and in the chronic constriction injury model as a model of neuropathic pain. Furthermore, the propensities of the compounds to produce analgesic tolerance, physical dependence, addiction (place conditioning paradigm), constipation and respiratory depression will be examined.